Traditionally, the joints between deck planks were caulked with hemp and tar or bitumen but the service life of such materials is very short and this system required constant renewal due to deterioration under the continual attack of the environmental agents. More recently modern materials have been used in an attempt to provide a satisfactory water tight weather resistant sealant. For such materials elastomeric sealants, in particular using synthetic plastics, polysulphides, synthetic rubbers and the like have been employed in order to provide caulking which is far removed from the old established traditional methods of caulking. British Pat. No. 883,924 describes a method of sealing joints between adjacent structural members, particularly between structural plates and the planks of a ship's deck using a sealing compound, which comprises first inserting into the joint a profiled strip of synthetic plastics material which has little adhesion to the sealing compound and then covering the strip with a sealing compound, the strip extending fully across the bottom of the joint and along the full length thereof. The sealing compound, however, is a hardenable material introduced into the gap in the fluid state.
Another approach to the problem of forming a seal between deck planks is discussed in British Pat. No. 711,332 in which a solid, resilient strip having a C-shape section (or part of the section) is inserted into a groove formed in a facing surface so as to be compressed when the planks are fitted together. In this system no hardenable fluid or curable material is used, and the resilient seal does not adhere to the adjacent edges of the planks. The seal is maintained by preliminarily compressing the strip so that expansion of the joint is taken up by the expansion of the preliminarily compressed strip. A similar system is disclosed in British Pat. No. 532,470.
One of the major problems in caulking deck planking lies in the fact that timber has a great propensity to dimensional variation due to changes in moisture content of the wood and movements up to 30% of the width of a sealed joint are not uncommon. Such movements are not easily accommodated by pre-compression as in the systems described in British Pat. No. 711,332. Modern elastomeric polymer materials have been found to provide suitable degrees of both resilience to accommodate dimensional variations and resistance to the salt water and wind, and other corrosive materials which may be found on a boat. The application of such modern materials to the narrow joints between deck planks has presented some problems, however, due to the fact that the long service life required of such materials can only be satisfactorily obtained provided the adhesive properties of the material are exploited between the caulking and the edge of the plank, and not in the general plane of the decking at the substrate level. Polymer materials used for such caulking are usually applied in a liquid or paste state and in order to prevent adhesion to the substrate it is necessary to perform a preliminary operation introducing into the bottom of the joint a suitable non-adhesive material or layer which will prevent the caulking material from adhering to the substrate. Such an operation is described in British Pat. No. 893,924. This operation must be performed with care in order to ensure that no masking of the edges of the planks is effected at the same time, which would detract from the ability of the caulking material to adhere to these edges. When applying the caulking material itself, great care must be taken to avoid any overlap of this onto the faces of the planks, and this is achieved either by the preliminary application of masking tape or strip to the planks in the vicinity of the joint edges, or by subsequent grinding or sanding operations effected to remove the surface layer of the plank and any adherent caulking. This is a very time-consuming and therefore costly process. Other disadvantages of the known materials include a short shelf life, a limited available working time(where two-part materials have to be mixed prior to use), which often results in wastage if the materials cannot be used in time, the possibility of air bubbles becoming introduced during application, and the lengthy curing time during which the material must not be disturbed. Curing times can often be as long as seven days.